The ‘Peak hour factor’ is defined as the ratio between the number of vehicles counted during the peak hour and _______ the number counted during the highest fifteen consecutive minutes.

Concept:

Peak Hour Factor (PHF):

It compares the traffic volume during the busiest 15 minutes of the peak hour with the total volume during the peak hour. It indicates how consistent traffic volume is during the peak hour.

\(Peak\space Hour\space Factor(PHF)= {Total\space hourly \space volume \over Peak\space 15\space minute\space volume\space within\space the\space hour \times 4}\)

The Highway Capacity Manual advises that in absence of field measurements reasonable approximations for peak hour factor can be made as follows:

• 0.95 for congested condition
• 0.92 for urban areas
• 0.88 for rural areas 

Hence, The ‘Peak hour factor’ is defined as the ratio between the number of vehicles counted during the peak hour and four times the number counted during the highest fifteen consecutive minutes.